Combretastatins having cis-stilbene as their basic skeleton are known to have strong cytotoxicity. However, because they are barely soluble in water, they have not been put to practical use as medicines. Therefore, various investigations to develop derivatives of these compounds have been made (Molecular Pharmacology 34, 200-206 (1988); J. Med. Chem., 34, 2579-2588 (1991); WO 92/16486; J. Med. Chem., ,35, 2293-2306 (1992); WO 93/23357; J. Med. Chem., 36, 2817-2821 (1993); Bioorg. Med. Chem. Let., 4, 699-704 (1994)), but compounds, which are effective in vivo are still unknown.